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Thursday, May 7, 2015

What the heck is a heat pump water heater and why should I care?

What the heck is a heat pump water heater and why should I care?

If you read my previous blog article
regarding the new Federal Energy Mandate (effective April 2015 ) regarding
electric water heaters, you would be well on your way to understanding why you
should care.The new 2015 DOE energy
efficiency mandates require higher EF ratings on most residential gas, electric
and oil fired water heaters. This will have impact how water heaters are
designed, manufactured, tested, distributed, and installed. It is my
understanding that the new energy mandate no longer allows for standard /
conventional electric water heaters over
approximately 55 gallons in size to be installed (simply because there are no
units available that meet the new energy requirements, but perhaps will be in
the future). This likely affects many
homeowners in my area, (Hilton Head Island, Bluffton, Beaufort, SC) since there
are so many 80 gallon tanks in service.

So, you wonder what you will have to
do to replace your electric water heater that is a 55 gallon capacity or
larger?Well, the most common options
are going to be “on-demand (tankless)” water heaters, and heat pump water
heaters, and possibly gas if you have provisions for gas. Let’s tackle one
thing at a time and look at heat pump water heaters and find out how they work
and the pros and cons.A future blog
will discuss “on – demand (tankless)” water heaters.

I know you probably like glossy
pictures, but how about just a basic diagram of a heat pump hot water
heater?

Heat pumps basically move heat from
one location to another. There, how simple an explanation can you get?Yes, there is a lot of wizardry going on in
these units, but it is always good to have a mystery in life.OK, so what else is special about how they
work, you ask.A heat pump water heater
moves heat from your basement or mechanical room into the hot water tank. This will
likely reduce humidity and lower the temperature in the area where the unit is
installed. This can be good in warm climates, but not so much in cold weather
climates. Heat pump water heaters have electric
heating elements installed (just like the conventional heaters they are
replacing) to compensate for large hot water demands. Most HPWH can normally
heat 8 gallons of water per hour. In comparison, a conventional electric unit
can heat 20 gallons per hour. Not to worry though, since most are going to
function in 3 to 4 different modes of operation:

“Hybrid Mode” – uses both electric
heating elements and the heat pump. This is the recommended setting and should be the default setting on units.

“Heat Pump Mode” – uses only heat
pump. Not a recommended setting as the hot water recovery time is considerably
diminished

“Full Electric Mode” – works just like
the dinosaurs they are replacing, (a
conventional electric hot water tank)

“Vacation Mode”- when on vacation,
puts unit into sleep mode, (not all units will have this feature)

If you are expecting a Co- mode, that
is a totally separate plumbing device. Quit interrupting me. On a more serious
note, please pay attention to the types of operating modes if you are
purchasing a heat pump water heater.

OK, you are wondering just how this
beast is controlled, aren’t you?Well,
lucky for you I have pretty picture of a typical controller. Study it well.

By now, I am hoping some of the
mystery is gone for you.But there are
other mysteries here to look at.

The Cons:

Heat pump water heaters have actually
been around for some time, but they were an add on to a conventional electric
water heater (imagine a large box next to a water heater).As you can see from the illustration above,
they are now neatly organized into one BIG container. Notice the emphasis on big.
That was intentional. These critters are much bigger than the dinosaurs they
are replacing (just one trade off). They
typically will require a large area to function properly (approximately 1000
square feet or more).They are also
heavier and larger (occupy more space) than a comparable electric water heater.
Can you guess that it will take more
people and expertise to install one? You would be correct. Oh, and let’s not
forget about maintenance, it will be more technical and expensive (remember the
days of changing your own elements or thermostats?). And finally, the cost. Yes
they will be more expensive. Enough, enough I say. No more negatives. Moving on
to the positives.

The Pros:

Testing
by the “Electric Power Research Institute”indicated that heat pump water heaters are 2.5 times more efficient than
conventional electric water heaters, and in addition draw less than 25% of the
electrical power compared to a conventional electric water heater. Water
heating accounts for 15 to 20% percent of electric energy use in homes with
electric water heating. Some new heat pump water heaters (HPWH) have
demonstrated savings of up to 50% or more of a home's water heating energy use
(perhaps under ideal conditions).

Units
will typically have user-friendly digital temperature controls with vacation
settings and options for operating modes.

Dehumidification
of the installation area and some cooling effect is possible. This may be a benefit
in warm climates but not cold climates. The amount of dehumidification and
cooling may also be minimal.

Adequate
physical space:heat pump water
heaters are generally larger in all dimensions) compared to standard water
heaters. Having limited physical space may prevent the water heater from being
installed in a desired location within a residence or where the conventional
water heater was installed.

Adequate air
volume and circulation: heat pump water heaters have specific air volume
and circulation requirements that can lower their performance if installed in a
confined sealed space, such as a closet or a small room.

Condensate
removal:access to a drain or to the outdoors is
required for removing the heat pump water heater’s condensate (liquid).
Typically, existing water heaters will have a drain pan, but additional piping
may be required for handling condensate removal. Also they will need an exhaust
line (piping) for the TPR (temperature pressure relief valve), just like the
conventional water heaters.

Noise:heat pump water heaters generate a
humming or whirring noise when operating. Depending on the heat pump water
heater model and location , this may be offensive.

Exhaust air:as
stated above, heat pump water heaters exhaust cool,
dehumidified air into their surroundings, which may or may not be beneficial.

Conclusion:

Hopefully
you are now better informed if you need to choose a water heater, however I
would urge you to do your homework and find out more about your choices. Fortunately
in our location, numerous 80 gallon tanks were installed not because the homes
or villas needed that capacity heater, but simply because the Electric Company
had a program that made it inexpensive to install one. I suspect a lot of folks
can do well just by reducing the size of their water heater when it is time to
replace it, and opting for a smaller capacity water heater (conventional).

One
more interesting piece of information to digest: the water heaters are not hot
water heaters. If the water is hot you do not need a heater, right? OK then,
that is settled. Note that the grammar police will not arrest you if you still
use the term “hot water heater”.

As a Home Inspector in Hilton Head, SC and surrounding areas, I
welcome your opinions, ramblings, musings, and fleeting thoughts.

6 comments:

I must thank you so much for this post as I almost went out and made a big mistake when it came to buying a new water heater. Ours gave up a few months ago and my wife begged me to go out and get a new one. I did not do my research so luckily I read your post.

Excellent post. I want to thank you for this informative read; I really appreciate sharing this great post. We are quality, knowledge Home & Real Estate Inspection for us. So Thank you so much for this post.Home inspections wellington